Heat exchange and method of making the same



Feb. 3, 1942. G, A, BRACE & 2,271,538

HEAT EXCHANGE AND METHOD OF MAKING THE SAME Filed April 25, 1958 INVENTOR 6201942 A, Brace ATTORNEY Patented Feb. 3, 1942 2,271,538 near sxcnaues ign METHOD or MAKING SAME George A. Brace, Winnetka, 111., assignor to The Hoover Company, North Canton, Ohio, a'cornotation of Ohio Application April 25, 1938, Serial No. 204,016

13 Claims.

This invention relates to heat exchange apparatus and more particularly-to finned tube heat exchange elements such as are commonly used as condensers, radiators, absorbers and for similar purposes.

It is a particular object of the invention to provide an improved method of making a finned tube heat exchange element. The patent to r A. J. Scholl 1,955,837, issued April 24, 1934, di'scloses a method of making a heat exchanger in which the fins and a serpentine tube are simultaneously moved together to secure the fins on the tube frictionally. This method provides a slotted fin heat exchanger in which the fins all bear the same relationship to the tube to which they are attached and there is no fin-tube contact area on one-half the tube circumference. With the method disclosed by the Scholl patent, the fins must be mounted in the supporting jig a distance apart equal to the distance between adjacent fins in the finished heat exchanger.

According to the present invention, there is provided a method of making a heat exchanger in which alternate fins are simultaneously applied to the serpentine tube from opposite sides thereof. The fin supporting jigsmount the fins a distance apartequal to twice the distance between adjacent fins in the finished product thereby providing a method of assembling a very close fin heat exchanger without requiring complex jigs tomount closely spaced fins.

The present method of making a heat exchanger also places the fins on the tube in symmetrical relationship as a result-of which all sides of the tube are symmetrically engaged by heat transfer elements.

Another important feature of the present method of making a heat-exchanger flows from the fact that the fins are slotted and are assembled on the serpentine tube by moving the slots over the tube but the slots on each fin are closed by a portion of an adjacent fin whereby the assemblin'g advantages of the slotted fin are combined with the heat transfer advantages of the axial type fin which is pierced by the tube elements of the heat exchanger.

bath which will firmly bind the fins to the tube and will also bond the slot closing elements to the edges of the slots thus giving the effect of a continuous fin which is pierced by a plurality of tube elements of a heat exchanger.

In previous methods of making slotted fin heat exchangers, the tube had to be supported at a 2 half the circumference After assembly of the fins on the tube, the assembly may be dipped in a soldering, tinning, brazing or like number of points in order to prevent deformity under the stress of the numerous fins being applied from the same direction. By the present method the ends of the tube need only be mounted in proper position andthe force to which the tube is subjected by each fin as it is applied to the tubeis balanced by an equal and opposite force applied by the adjacent fins as those fins are applied to the tube.

:Previous finned tube heat exchange elements have in general been of two types; that is, the slotted type fin which is mounted on the tube by positioning the tube in a slot extending from one edge of the fin to substantially the center 5 thereof, as exemplified by the patent to Scholl,

or the axial type fin which is provided with a central opening and is slid onto the tube until it reaches its proper position. The slotted type fin has the disadvantage that it embraces only of the heat exchange tube and for a length equal only to the thickness of the fin. This resultsin an unsymmetrical heat transfer between the tube and the fin and also provides only a very small direct transfer area between the tube and the fin. Also, all

portions of the tube not directly contacted by the edge of the fin are without heat rejecting elements.

The axial fin provides continuous symmetrical 0 contact between the fin and the tube but again ous disadvantage of the axial type fin resides in the. fact that one fin cannot contact more than a single element of a multi-pass heat exchanger unless the tube are inserted individually through their respective holes in the fin and are then joined at their ends by some type of a return bend structure.

,# The slotted type fin is readily mounted 'on the heat exchange tube but heretofore all have been mounted on the same side of the'tube thereby limiting the minimum spacing between adjacent fins and also requiring very costly and extremely accurate jigs for supporting closely spaced fins prior to insertion on the heat exchanger tube.

The axial type fin is very vdiiiicult to assemble 9 on the heat transfer .tube for the reason that it must be moved axially ,along the tube from the end thereof to its final position which might entail moving an individual fin almost the entire length of the tube; as a result of this, the

opening through the fin may become enlarged during the assembling process with resulting poor heat contact with the exterior wall of the tube. This type fin also requires very accurate positioning jigs and fin-mounting apparatus. Furthermore, the axial fin type required that the individual finned tubes be connected in some manner to other finned tubes.

Accordingly, it is an object of this invention to provide a heat exchanger including a multipass heat transfer conduit which is provided with 'fin elements completely surrounding the heat transfer conduit but which may be mounted on the tube from the side thereof, which has coninuous heat transfer contact with the heat transfer tube lengthwise thereof and extending over one-half the circumferential area of the tube, and to provide a fin structure for heat transfer elements which is continuous and in which the individual fins may be spaced in very close relationship without undue complication of manufacturing dies and assembling jigs.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawing in which:

Figure 1 is an isometric view of a heat exchanger embodying my invention.

Figure 2 is a fragmentary exploded view partly in section of a heat exchanger embodying the invention.

Figure 3 is an isometric view of one of the fin elements forming part of my invention.

Figure 4 is an isometric view of a modified form of the invention, and

Figure 5 is a perspective view illustrating the method of assembling the heat exchanger forming the subject matter of this application.

Referring now to'the drawingand first to Figures 1 to 3 thereof, the heat exchange element will be described in detail.

The heat exchange element comprises a continuously reversely bent tube indicated generally at II which may be made of any desired material and cross-sectional configuration. As shown, the tube II is reversely bent to provide three parallel serially connectedconduit sections I2. The tube II is provided with a plurality of air cooling fins designated a, b, a, b, etc. throughout the length of the individual conduits I2 for a reason to be developed hereinafter. Each fin a or b is in contact with every one of the individual conduits I2 of the tube I I.

In order to prevent heat transfer lengthwise of the fin from oneconduit I2 to an adjacent conduit which ordinarily is at a different temperature, the fins a and b are provided with at right angles to the edge portion of the fin a opposite to the edge into which the slot I6 opens.

The fins b are identical-with the fins a, but are rotated through an arc of 180. Thus, each fin b is provided with slots I5 corresponding'to the slots I6, semi-cylindrical collars I'I corresponding to the collars I8, tongue elements I9 corresponding to the tongue elements 20, and slots I4 corresponding to slots I4 of the fins a.

One of the fins b is shown singly in Figure 3 but it is turned end for end with respect to its position in Figures 1 and 2 to illustrate the construction thereof. It will be understood that the fins a are structurally identical with the fins b, and that they are merely rotated in their own planes through arcs of 180 prior to assembly on the tube I I.

When the apparatus is assembled, the downwardly opening tube receiving slots I6 of each fin -a are closed by the downwardly extending tongues I9 on an adjacent fin b, and the upwardly extending tube-receiving slots I5 of each fin b are closed by the upwardly extending tongues 20 of an adjacent fin a. Therefore, each conduit element I2 is completely surrounded by substantially continuous fin elements and the areas of the conduit elements between adjacent fins are snugly embraced over one half their surfaces by collar elements I1 and I8. The conduits are alternately embraced by upwardly and downwardly facing collar elements I1 and I8, respectively.

After assembly, the heat exchanger may be dipped in a tinning, soldering, brazing or like bath to-bond the fins a and b and the collars I1 and I8 to the conduits I2. This operation also bonds the tongues I9 and 20 to the edges of the slots I6 and I5, respectively, thereby completely surrounding each conduit element with a continuous fin surface.

It follows from the construction just described that a multi-pass heat exchange element is formed having unit structures which completely surround each pass of the heat exchange element, which are sufficiently separated to prevent heat transfer between adjacent passes of the heat exchange element through the fins, and which are provided with a means extending over a large area of the tube and formed integrally with each fin element to transfer heat therebetween whereby a highly eflicient heat transfer Y .fin structure is provided.

deep slots I4 between adjacent tube elements I2. The fin element a is provided with a plurality of spaced apart parallel slots I6 extending from the edges thereof to substantially their central portions. The material which is removed to form these slots is bent outwardly at substantially right angles to the plane of the fins a for a.distance equal to the desired spacing between adjacent fins a and b and is curved to form semi-cylindrical collar elements I8 which are adapted to engage closely the conduit elements I2. Preferably, the slots I6 are slightly narrower than the diameter of conduit II so that when the fins are pressed upon the conduit, the fins bite into the conduit. The end portion of'each collar I8 is provided with a tongue 20, also formed from the material removed to form the slot I6, which tongue extends at right angles to the collar I8 and terminates in a plane formed it is simpler and cheaper to manufacture.

In Figure 4 there is disclosed a modified form of the invention. The tube and conduit elements II" and I2 are identical with the elements I I and I2, respectively, previously described. The

fin elements a and b are identical with the fin elements a and b previously described with the exception that the tube engaging collars I1 and I8,and the interfitting tongues I9 and 20 are-omitted. This form of heat exchanger does not provide the extensive fin-tube contact area characteristic of-that previously described, but This construction has all the advantages of the form shown in Figures 1 to 3 except those flowing from the presence of collars I1 and I8, and tongues I9 and 20;

The form of the invention disclosed in Figures 1 to 3 may be manufactured from sheet stock by stamping out the slots I4, cutting or stamping the edges of the slots I5-I6 and forming the collars I'I-I8 and tongues Iii-2,0 in a die from the material filling the slots I5I6.

plates 25 and 26 which are hingedly connected together by a pintle 21, the free ends of each of the elements 25 and 26 are provided with a plurality of fin receiving slots 28 which terminate a relatively great distance from the pivotal axis of the jig. The individual fin elements may simply lie in the slots 28 or, if desired, light springs may be provided in the slots to engage the sides of the fins, or those portions of the slots not occupied by the fin may have a locking plate inserted therein; however, it is desirable that the fins merely rest in the slots by gravity. All the fins a are mounted in one of the plates 25, 26 and all the fins b are mounted in the other of said plates, as shown the fins a are in the plate 25 and the fins b are in the plate 26. The slots 28 are spaced a distance apart equal to twice the desired spacing between adjacent fins on the completed heat exchange element and the slots in one plate are staggered a distance equal to the distance between adjacent fin elements from the slots in the cooperating fin supporting plate. When the fins have been inserted in the plates 25 and 26, these plates are pivoted about the pintle 21 by any desired mechanism and the slots l5 and It then receive the various conduit elements l2 of the tube II in proper position. The slots l5 and I6 may be very slightly smaller than the diamcter of the conduit ll so that the fins will frictionally engage the conduit and will remain thereon when the plates 25 and 26 are pivoted away from each'other.

The distance between the bottoms of the slots 28 and the pintle 21 is relatively great whereby the fins move over a short are on a large radius in engaging the tube l I. Due to this construction the edges of the slots in the fins may be normal to the edges ofthe fins even though the fins move in a small are when being assembled on the tube. The actual curvature of the small are through which the fins move is so small that it approaches a straightline condition for all practical purposes, and'the edges'of the slots need not be cut on an arc.

Due to the fact that the fins are appliedto the tube simultaneously from opposite sides thereof, any forces-produced by the reaction between the tube and thefins tending to deform the tube are neutralized and the tube need not be supported by heavy rigidifying elements.

The invention herein disclosed provides a heat exchange element having symmetrical fin contact areas onall conduit sections, single fin elements which engage completely around individualco'nduit elements of a multi-pass heat exchanger and which may be assembled on the tube from the side thereof. Additionally, in one form of,the invention. each individual fin element cooperates to complete the conduit receiving cut-out of an adjacent fin element and has an elongated portion engaging a large area lengthwise of the conduit elements of the heat exchanger to provide an integral heat transfer path between the body of the-fin proper and such large tube area.

Furthermore, the fins may be mounted upon the conduit element in very closely spaced relationship without requiring that the individual assembling supports for the fins be constructed to mount the fins in close relationship.

A particularly advantageous feature resides in the fin structure and method dfassembly whereby the fins are assembled simultaneously from opposite sides of the conduit elements of the heat exchanger, and the fin-conduit contact areas are symmetrical.

The present invention provides a fin structure for multi-pass heat exchangers having a continuous reversely bent tube element which combines the assembling advantages of the side slotted fin and the heat transfer advantages of the axial fin with a structure having extensive and continuous fin-tube contact areas throughout the finned area of the tube.

While the invention has been disclosed herein in-detail, it is not limited thereto, various changes may be made in the arrangement, proportion,

and construction of the paths without departing from the spirit thereof or the scope of the appended claims.

I claim: 1. The method of forming a heat exchange element comprising, severing a plurality of geometrically shaped fins on substantially parallel lines of severance extending from the edge toward the geometrical center thereof, bending the material between the severance lines away from the body of the fins and reversely of the direction of the severance lines to form fins having slots extending to the edge thereof and lateralextensions at the base of the slots having reversely bent portions extending in a direction opposite that of the slots, supporting the fins in two group's with the fins of one group spaced laterally ofthose of the other group a distance substantially equal to the length of the lateral extensions and with the slots of each group facing those of the other group, supporting a fluid conduit between the groups in line with the slots, and applying the fins to the fluid conduit with the fins of each group interleaving with the fins of the opposite group by bringing the groups toward each other to force the slots over the fluid conduit, the lateral extensions into heat exchange relationship therewith, and the reversely bent portions of one group into the unfilled'portions of the slots of the other group.

2. The method of making a heat exchanger comprising forming a tube into a continuous serpentine coil having a plurality of spaced straight runs connected by returnbends, severing a plurality of fins on substantially parallel lines from the edge toward the center thereof at spaced areas corresponding to the spacing of the straight runs of the coil and toe. depth in excess of the diameter of the coil, bending the material between the severance lines away from the body of the fins and reversely toward the uncut edge of the fins to form fins having slots corresponding in number to the number of spaced runs extending to the edge of the fins and a corresponding number of lateral extensions and reversely bent portions extending to the unsevered edge of the fins opposite the slots, supporting the fins in two groups on opposite sides of the straight runs of the coil with the slots of each group facing those of the other group and with the fins of one group spaced from those of the other group longitudinally of the straight runs of the coil a distance substantially equal to the length of the lateral extensions, and bringing the groups toward each other to force the slots over the straight runs of the coil, the lateral extensions into heat exchange relationship therewith and the reversely bent portions of one group into the unfilled portions of the slots of the other group.

3. The method of forming a heat exchange element comprising severing a plurality of geometrically shaped fins on substantially parallel severance lines extending inwardly from the edge thereof, bending the material between the severance lines away from the body of the fins to form fins having open slots and integral lateral extensions, supporting the fins in two groups with the open slots of each group facing those of the other group and with the fins of one group spaced from those of the other group a distance substantially equal to the length of the lateral extensions in the direction of said extensions, supporting a fiuid conduit between the groups at the open slots thereof and bringing the groups toward each other to apply the fins of each group to the conduit in interleaving relationship with the fins of the opposite group by forcing the slots of each group into frictional engagement with the conduit and the lateral extensions into heat exchange relationship therewith.

4. A heat exchanger comprising a conduit element, and a plurality of heat transfer elements attached to the exterior surface of said conduit, said heat transfer elements having slots for receiving said conduit element to a depth sufficient to cause said heat transfer elements to project from opposite sides of said conduit element, the slots in adjacent heat transfer elements extending in opposite directions, each of said heat transfer elements including an integral conduit contacting element extending in the direction of an adjacent heat transfer element, each of said conduit contacting elements being provid d with an angularly extending tongue element engaging in open portion of the conduit receiving slot formed in an adjacent heat transfer element which extends beyond said conduit.

5. A heat exchanger comprising a continuous serpentine coil having a plurality of straight portions connected by return bends, spaced elongated fins having an open ended slot for each straight portion mounted on said coil with the edges of the slots in frictional engagement with the walls of said straight portions, said slots being of a depth at least as great as the diameter of said coils and the slots of each alternate fin extending in opposite directions and each of said fins having cut-out portions between the adjacent straight portions of the coil to resist heat transfer along the length of the fin.

6. A heat exchange device including a conduit and a plurality of strip fins each having a plurality of notches along one edge thereof bridging said conduit, integral conduit engaging elements extending laterally from the notches in each fin and snugly embracing the conduit, said conduit engaging elements extending substantially the full distance between adjacent fins, and an integral tongue on the end of each conduit engaging element filling the open portion of the conduit receiving notch in an adjacent fin.

7. The method of making a refrigerator element which comprises forming a'tube into a continuous serpentine coil having more than one bend and alternate straight runs, supporting a plurality of fins having slotted edges in two groups with the fins of each group in spaced relationship on opposite sides of the coil with the slots extending in opposite direction towards the straight runs and with the fins of one group spaced longitudinally of the runs relative to those of the other group and simultaneously applying the fins of the two groups to the coil in interleaving relationship by forcing the slots of all of said fins and the runs of the coils together by pressure applied to the sides of the fins of each group opposite the slots to cause a frictional Jointure of the coil and fins.

8. The method of making a heat exchange element comprising severing the material of a plurality of fins at two spaced substantially parallel lines extending to theedge of the fins, bending the material between the lines at right angle to the body of the fins to form fins having a slot extending to the edge thereof with an extension at right angles to the body of the fins, supporting the fins in two groups with the slots of one group extending towards those of the other group and with the fins of one group spaced from those of the other group in the direction of the right angled extensions, positioning a fiuid conduit between the groups at the slots and simultaneously applying pressure to the sides of each group of fins opposite that of the slots to press the slots into frictional engagement with the fluid conduit with the extensions of the fins of one group extending to the bodies of the fins of the other group.

9. The method of makinga heat exchange element comprising forming a tube into a continuous serpentine coil having alternate return bends and straight portions, supporting a plurality of spaced fins having deep open ended slots in two groups on opposite sides of said coil with the slots facing the coil and simultaneously applying pressure to each group to force the slots into frictional engagement with the coil and to cause the fins of each group to extend beyond the coil to a position such that the fins of one group alternate with the fins of the other group and such that the corresponding edges of all fins are in substantial alignment.

10. The'method of manufacturing a heat exchanger of the type including a serpentine coil having a plurality of parallel runs connected by return bends and fins having slots receiving each of said straight runs which includes the steps of cutting slots inwardly from the edges of the fins and at right angles thereto to a depth such that the fins will extend on opposite sides of the coil when the parallel runs thereof are positioned in the slots, supporting groups of fins on opposite sides of said coil against lateral displacement and with the slots in adjacent fins facing oppositely and simultaneously applying the fins to the coil with the fins of each group interleaving with the fins of the opposite group by forcing the slots over the fins by applying oppositely directed forces to each group of fins and constraining the fins to move along an are having a radius of curvature which is very large as compared with the depth of the fin slots.

11. That method of applying slotted fins to a serpentine heat exchanger coil without subjecting the coil to deforming forces which includes the steps of supporting the coil at its ends, supporting groups of fins having coil receiving slots of a depth such that each fin will extend onopposite of the coil when assembled therewith on opposite sides of said coil and in staggered relationship with the slots of each group,

opening toward the coil, and applying cppesitelg directed forces to the oppositely facing groups transfer elements extending in opposite direcof fins to force the slots in the fins over the coil tions.-

to effect a frictional jointure therebetween, the 13. A heat exchanger comprising a conduit,-

forces applied to the coil .by each fin being baland a plurality of heat transfer elements atanced by equal and opposite forces applied by the tached to the exterior surface of said conduit, adjacent oppositely facing fins. said heat transfer elements having slots the edges 12. A heat exchanger comprising a conduit, of which engage said conduit and being of such and a plurality ofheat transfer elements atdepth that the body of the heat transfer eletached to the exterior surface of said conduit, ments extend on opposite sides of the conduit, said heat transfer elements having slots the 10 the slots in alternate heat transfer elements exedges of which engage said conduit in heat contending in opposite directions, each of said heat ducting frictional relationship therewith and transfer elements including an integral conduit said slots being of such depth that the body of contacting element extending in the direction of the heat transfer elements extend on opposite an adjacent heat transfer element. sides of the conduit, the slots in alternate heat 15 GEORGE A. BRACE. 

